Xenophon threatening defamation action

Mr Xenophon is angry about comments Mr Marshall made that SA-Best had "done a deal" with Labor to target opposition-held seats to prevent a Liberal majority government after the March 17 South Australian election.

Mr Xenophon said the statements were "totally false" and "defamatory".

"Accordingly this morning I have issued a concerns notice to Mr Marshall, pursuant to the Defamation Act," Mr Xenophon said in a statement.

Mr Marshall said on Tuesday it was his "strongly held belief" a deal had been done by Labor and SA-Best for Mr Xenophon to target Liberal-held seats.

"The reality is all the evidence supports this," Mr Marshall said on Tuesday.

SA-Best has announced its intention to run in around 30 seats in the lower house in a bid to hold the balance of power.